The 19 October 1987 global stock-market crash is known as Black Monday.
The Dow Jones Industrial Average fell 508 points, or 22.6%, on 19 October 1987. That remains its largest one-day percentage decline. Stock markets in other countries also dropped sharply, making the event international rather than solely American.
Several factors contributed, including high valuations, worries about interest rates and trade deficits, and widespread use of computerized trading strategies. Portfolio insurance programs were designed to limit losses, but their selling orders intensified the downward movement as prices fell.
Black Monday is often confused with the Wall Street Crash of 1929, which unfolded over several trading days and helped precede the Great Depression. The 1987 crash did not produce an equivalent decade-long economic collapse, partly because central banks and financial institutions responded quickly.